AbsolutePosition and CursorLocation Properties Example (VC++)
This example demonstrates how the AbsolutePosition property can track the progress of a loop that enumerates all the records of a Recordset. It uses the CursorLocation property to enable the AbsolutePosition property by setting the cursor to a client cursor.
#import "C:\Program Files\Common Files\System\ADO\msado15.dll" \
no_namespace rename("EOF", "EndOfFile")
#include <ole2.h>
#include <stdio.h>
#include "conio.h"
#include "AbsolutePositionX.h"
//Function Declarations
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void AbsolutePositionX(void);
void AbsolutePosition2X(void);
void PrintProviderError(_ConnectionPtr pConnection);
///////////////////////////////////////////////////////////
// //
// Main Function //
// //
///////////////////////////////////////////////////////////
void main()
{
if(FAILED(::CoInitialize(NULL)))
return;
AbsolutePositionX();
//Clear the screen for the next display
printf("Press any key to continue...");
getch();
system("cls");
AbsolutePosition2X();
::CoUninitialize();
}
///////////////////////////////////////////////////////////
// //
// AbsolutePositionX Function //
// //
///////////////////////////////////////////////////////////
void AbsolutePositionX(void)
{
HRESULT hr = S_OK;
// Define ADO object pointers.
// Initialize pointers on define.
// These are in the ADODB:: namespace.
_RecordsetPtr pRstEmployees = NULL;
//Define Other Variables
//Interface Pointer declared.(VC++ Extensions)
IADORecordBinding *picRs = NULL;
CEmployeeRs emprs; //C++ class object
_bstr_t strMessage;
char chKey;
//Open a recordset using a Client Cursor
//For the Employee Table
_bstr_t strCnn("Provider=sqloledb;Data Source=srv;"
"Initial Catalog=Pubs;User Id=sa;Password=;");
try
{
//Open a recordset.
TESTHR(pRstEmployees.CreateInstance(__uuidof(Recordset)));
//Use client cursor to enable AbsolutePosition property.
pRstEmployees->CursorLocation = adUseClient;
//You have to explicitly pass the default Cursor type
//and LockType to the Recordset.
TESTHR(pRstEmployees->Open("employee",
strCnn,adOpenForwardOnly,adLockReadOnly,adCmdTable));
// Open an IADORecordBinding interface pointer which we'll use
// for Binding Recordset to a class.
TESTHR(pRstEmployees->QueryInterface(
__uuidof(IADORecordBinding),(LPVOID*)&picRs));
//Bind the Recordset to a C++ Class here
TESTHR(picRs->BindToRecordset(&emprs));
strMessage= "";
//Enumerate recordset
do
{
//Display Current Record Information
printf("Employee : %s \n record %ld of %d",
emprs.lau_lnameStatus == adFldOK ?
emprs.m_szau_lname : "<NULL>",
pRstEmployees->AbsolutePosition,
pRstEmployees->RecordCount);
printf("\nContinue?(y/n) :");
do
{
chKey = getch();
}while(chKey != 'y' && chKey !='n');
//Clear the Screen for the next output
system("cls");
if(chKey == 'n')
break;
strMessage = "";
pRstEmployees->MoveNext();
}while(!(pRstEmployees->EndOfFile));
// Clean up objects before exit.
pRstEmployees->Close();
//Release the IADORecordset Interface here
if (picRs)
picRs->Release();
}
catch(_com_error &e)
{
// Notify the user of errors if any.
_bstr_t bstrSource(e.Source());
_bstr_t bstrDescription(e.Description());
PrintProviderError(pRstEmployees->GetActiveConnection());
printf("Source : %s \n Description : %s \n",
(LPCSTR)bstrSource,(LPCSTR)bstrDescription);
}
}
///////////////////////////////////////////////////////////
// //
// AbsolutePosition2X Function //
// //
///////////////////////////////////////////////////////////
void AbsolutePosition2X(void)
{
HRESULT hr = S_OK;
// Define ADO object pointers.
// Initialize pointers on define.
// These are in the ADODB:: namespace.
_RecordsetPtr pRstEmployees = NULL;
//Define Other Variables
//Interface Pointer declared.(VC++ Extensions)
IADORecordBinding *picRs = NULL;
CEmployeeRs emprs; //C++ class object
_bstr_t strMessage;
char chKey;
//Open a recordset using a Client Cursor
//For the Employee Table
_bstr_t strCnn("Provider=sqloledb;Data Source=dhale1;"
"Initial Catalog=Pubs;User Id=sa;Password=;");
try
{
//Open a recordset.
TESTHR(pRstEmployees.CreateInstance(__uuidof(Recordset)));
//Use client cursor to enable AbsolutePosition property.
pRstEmployees->CursorLocation = adUseClient;
//You have to explicitly pass the default Cursor type
//and LockType to the Recordset.
TESTHR(pRstEmployees->Open("employee",
strCnn,adOpenStatic,adLockReadOnly,adCmdTable));
// Open an IADORecordBinding interface pointer which we'll use
// for Binding Recordset to a class.
TESTHR(pRstEmployees->QueryInterface(
__uuidof(IADORecordBinding),(LPVOID*)&picRs));
//Bind the Recordset to a C++ Class here
TESTHR(picRs->BindToRecordset(&emprs));
long lGoToPos = 21;
pRstEmployees->AbsolutePosition = (PositionEnum)lGoToPos;
//Display Current Record Information
printf("Employee : %s \n record %ld of %d",
emprs.lau_lnameStatus == adFldOK ? emprs.m_szau_lname :
"<NULL>", pRstEmployees->AbsolutePosition,
pRstEmployees->RecordCount);
printf("\nPress any key to continue:");
getch();
// Clean up objects before exit.
pRstEmployees->Close();
//Release the IADORecordset Interface here
if (picRs)
picRs->Release();
}
catch(_com_error &e)
{
// Notify the user of errors if any.
_variant_t vtConnect = pRstEmployees->GetActiveConnection();
// GetActiveConnection returns connect string if connection
// is not open, else returns Connection object.
switch(vtConnect.vt)
{
case VT_BSTR:
printf("Error:\n");
printf("Code = %08lx\n", e.Error());
printf("Message = %s\n", e.ErrorMessage());
printf("Source = %s\n", (LPCSTR) e.Source());
printf("Description = %s\n", (LPCSTR) e.Description());
break;
case VT_DISPATCH:
PrintProviderError(vtConnect);
break;
default:
printf("Errors occured.");
break;
}
}
}
///////////////////////////////////////////////////////////
// //
// PrintProviderError Function //
// //
///////////////////////////////////////////////////////////
void PrintProviderError(_ConnectionPtr pConnection)
{
// Print Provider Errors from Connection object.
// pErr is a record object in the Connection's Error collection.
ErrorPtr pErr = NULL;
long nCount = 0;
long i = 0;
if( (pConnection->Errors->Count) > 0)
{
nCount = pConnection->Errors->Count;
// Collection ranges from 0 to nCount -1.
for(i = 0; i < nCount; i++)
{
pErr = pConnection->Errors->GetItem(i);
printf("\t Error number: %x\t%s",
pErr->Number,(LPCSTR) pErr->Description);
}
}
}
AbsolutePositionX.h:
#include <ole2.h>
#include <stdio.h>
#include "icrsint.h"
//This Class extracts lastname.
class CEmployeeRs : public CADORecordBinding
{
BEGIN_ADO_BINDING(CEmployeeRs)
//Column lname is the 4th field in the recordset
ADO_VARIABLE_LENGTH_ENTRY2(4, adVarChar, m_szau_lname,
sizeof(m_szau_lname), lau_lnameStatus, TRUE)
END_ADO_BINDING()
public:
CHAR m_szau_lname[41];
ULONG lau_lnameStatus;
};